In recent years, there have been proposed and developed various variable displacement vane pumps capable of varying a discharge of working fluid, usually expressed as a fluid flow rate per one revolution of a vane-pump rotor. One such variable displacement vane pump has been disclosed in Japanese Patent Provisional Publication No. 05-79469 (hereinafter is referred to as “JP5-079469”). The variable displacement vane pump disclosed in JP5-079469, has a control oil chamber defined between the inner periphery of a vane-pump housing and the outer periphery of a cam ring and partitioned by a cam-ring pivot pin fixedly connected to the pump housing and a seal member attached to the outer periphery of the cam ring. The eccentricity of the cam ring with respect to the vane rotor, exactly, the distance from the axis of rotation of the vane rotor to the geometric center of the cylinder bore of the cam ring, can be controlled or adjusted by varying a hydraulic pressure supplied into the control oil chamber, thereby varying the discharge of the vane pump.
However, to produce an oscillating motion of the cam ring pivoted to the pivot pin, the variable displacement vane pump of JP5-079469 requires the previously-noted oil control chamber defined between the pump-housing inner periphery and the cam-ring outer periphery and partitioned by the pivot pin and the seal member. The disadvantages of the variable displacement vane pump of JP5-079469 are the difficulty of reducing the number of component parts constructing the variable displacement vane pump assembly and the increased vane pump manufacturing costs.
Thus, it would be desirable to provide a variable displacement vane pump of reduced number of component parts.